Hosts show Check_MK service for SNMP monitoring as "CRIT" "Null"

Honestly I ended up rolling back to the stable 2.0 release (think it was p22 or something) since 2.1 seems to be a work in progress. (almost overheated my test lab laptop)

Make sure you have “no snmp” and “no agent” configured for the host to only do ping checks, this should clear up the CRIT or WARN state if its in one.